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MIMEDefang, a sendmail milter written by Roaring Penguin Software, filters all e-mail messages sent via SMTP through a sendmail installation, blocking common mail viruses, and now – with the help of SpamAssassin – spam. "You can use SpamAssassin to test for spam, and then all of the MIMEDefang goodies to reject, manipulate or otherwise mangle the message." Integrated with the MTA to the level of returning 5xx error codes during the SMTP session, so viruses or detected spam can be rejected at the delivery, which notifies the sender, that the mail was rejected, without generating an additional email message.http://www.mimedefang.org/
NOTE: spamass-milt has not been updated in a long time and is subject to a serious security problem. http://seclists.org/fulldisclosure/2010/Mar/140 If you want to use SpamAssassin as a milter, choose something other than spamass-milt.
spamass-milt http://savannah.gnu.org/projects/spamass-milt/ is a sendmail milter by Georg C. F. Greve, which allows sendmail users to filter spam at the heart of the sendmail message pipeline. It also allows SpamAssassin to be used for UUCP sites. If you plan to use this, be sure to read Kevin McGrail's walkthrough at Peregrine Hardware. http://www.peregrinehw.com/downloads/SpamAssassin/INSTALL-spamassmilter.
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